Telephones are commonly found in homes and in businesses. Such telephones may be combined in a full duplex telephone system, such as shown in FIG. 1, in which various users at different telephones (e.g., users A, B, C) can hear each other and speak to each other simultaneously.
In the configuration of FIG. 1, user A is a full duplex unit 20A coupled by two cables, 30AB/BA and 30AC/CA, to two units, namely units 20B and 20C, which are associated with users B and C respectively. By contrast, units 20B and 20C are each shown coupled by a single cable (e.g, 30AB/BA, 30AC/CA) to only one unit, namely unit 20A associated with user A. Units 20A, 20B, 20C communicate with each other through an analog or digital phone network 40, and hardware-implemented bridge circuitry 50. Bridge circuitry 50 enables each user to speak with and listen to each other user. Thus, user B can communicate with user C, notwithstanding that user B and user C are connected to user A. The "AB/BA" and "AC/CA" nomenclature associated with the telephone cables denotes their multi-directional nature, and indeed each telephone cable includes several wires.
Thus, although unit 20A must be a full duplex two line unit, unit 20B and unit 20C may be single line non-full duplex units, as shown. As such, unit 20A will include a two line personal computer ("PC")/speaker phone and full duplex modules. As used herein, "PC/speaker phone" may include a telephone, a speaker telephone, a PC coupled to a telephone, and a PC coupled to a speaker telephone.
Although unit 20B and/or unit 20C may be equipped similarly to unit 20A, it suffices if unit 20B and/or unit 20C are ordinary single line, telephone units. Unit 20A (which may, but need not be identical to units 20B and/or 20C) includes a host computer system 60 comprising a central processor unit ("CPU") 70, and memory 80. One or more software programs 90 may be stored or loaded into memory 80 for execution by CPU 70.
Unit 20A includes a first module 100AB associated with cable 30AB/BA coupling units 20A and 20B, and further includes a second module 100AC associated with cable 30AC/CA coupling units 20A and 20C. Of course, if unit 20A were coupled to additional units, there would be additional cables and modules. Each module 100AB, 100AC preferably includes a modem (e.g., 110AB, 110AC), a speaker phone unit (e.g., 120AB, 120AC), and an acoustic echo canceller ("AEC") unit (e.g., 130AB, 130AC).
Modem 110AB couples speaker phone 120AB to telephone cable 30AB/BA, while modem 110AC couples speaker phone 120AC to telephone cable 30AC/CA. The speaker phone provides the functions of dialing, and includes a sound system 140, a loudspeaker 150, and a microphone 160.
It is the function of the AEC units to prevent a target user from hearing his or her own echo emanating from a sending unit. Thus, AEC 130AB will prevent user B from hearing an echo of his or her own voice on the signal received from unit 20A. AEC functions may be carried out for convenience in the associated modems within each speaker/telephone.
Sound system 140 interfaces signals from host computer unit 60 to loudspeaker 150 and microphone 160. Loudspeaker 150 reproduces sounds generated by units 20B and 20C, while microphone 160 picks up the voice of user A as well as other audible sounds within the environment of unit 20A. Unfortunately, such other audible sounds can include echoes of signals from user B and user C. These echoes can result from soundwaves emanating from speaker 150 bouncing off walls and other objects within the room or environment containing unit 20A. In similar fashion, microphones associated with units 20B, 20C may detect and couple into their respective units echoes of signals from users A and C, or from users A and B.
It is the function of bridge unit 50 to enable each user to hear all parts of a conversation. Thus, user A can hear user B and/or user C, B can hear user A and/or user C, and user C can hear user A and/or user B. As noted, user B and user C may communicate with each other and with user A, notwithstanding that only unit 20A is required to be a full duplex two line unit. Bridge unit 50 is commonly implemented in hardware and operated under control of host computer system 60 as shown by control line 170.
Somewhere within system 10 physical space must be provided to mount the circuitry implementing bridging unit 50. In some systems, bridging circuitry is implemented on a common printed circuit board as a modem, perhaps modem 110AB. But the resultant printed circuit board then becomes a customized rather than a generic commodity, with resultant increased manufacturing cost.
The precise location of bridging unit 50 can affect hardwiring with the various telephone cables 30AB/BA, 30AC/CA. Frequently the circuitry implementing unit 50 is complex, especially if telephone network 40 is digital rather than analog. A digital network requires that bridging circuitry 50 accommodate and understand the protocol of the various digital signals. Further, the bridging circuitry must also identify the source of each user's voice and must sum these voices mathematically in the digital realm. While the cost of analog or digital bridging circuitry is perhaps $30 or less, it would be desirable to eliminate the cost altogether. Understandably, it would be advantageous to eliminate the requirement to provide physical space somewhere within system 10 to locate bridging unit 50.
Thus, there is a need for a bridging system for use in a full duplex telephone system that does not require hardware implementation. Preferably such a bridging system should be implemented in an inexpensive fashion, using conventional components and techniques.
The present invention discloses such a bridging system for use in a full duplex telephone system.